If you die without a will, the probate process kicks in and the state will name a personal representative (the person who will distribute your assets). In most cases, the surviving spouse gets that difficult job. Naming a representative can get complicated when you add in ex-spouses, kids, parents and even that oddball uncle who thinks you were best buds.
Until the courts decide who will distribute your assets, they will be frozen. That means no one can touch your stuff, even if you said they could have it. And even after the court names a representative, family and friends might resent the person who was chosen.
If nobody is willing to handle your estate, the courts will name a public trustee. This total stranger will distribute your assets according to the laws in your state - that usually leaves everybody unhappy.